1. Field of the Invention
This invention relates to a fluid control valve and, in particular, to a gas regulator valve useful with gas fired appliances such as space heaters.
2. Brief Statement of the Prior Art
Gas supply control valves for appliances such as space heaters have operating characteristics which are closely specified by the American Gas Association. These operating characteristics have resulted in a fairly common valve design such as illustrated in U.S. Pat. Nos. 3,685,732 and 3,513,873. The valves typically have a housing with inlet and outlet ports separated by a valve member carried on a diaphragm actuator with the opening side of the diaphragm pressured with the gas pressure of a bleed chamber within the housing. The bleed chamber receives the supply gas through a bleed orifice and communicates with the exit port through a snap-acting, heating-demand valve and a pressure regulator valve. The latter has a diaphragm valve actuator and responds to the gas pressure in the exit port of the valve.
The aforedescribed valve structure has a snap opening characteristic and is either off or on, supplying gas at a predetermined, controlled supply pressure. Improvements of the basic structure of these valves have provided a throttled or reduced pressure gas supply upon initial opening of the valve; see U.S. Pat. Nos. 3,354,901 and 3,502,101. This is desirable to establish convection currents in the flue of the appliance before the appliance burner is fully on, thereby avoiding the possibility of flame rollout or other difficulties maintaining combustion of the burner. These valves typically exhibit a step opening characteristic by flow restricting orifices in various internal passageways which control the pressure development in operating chambers of the valves. The flow restricting orifices, however, limit the reset time of the valves. Sudden variations in heating demand such as a rapid opening and closing of the thermostat contacts can exceed the reset capability of these valves, with consequential loss of step opening.